What is the physics behind conventional and reverse swing of a cricket ball ?

I know about reverse swing upto some depth, as one side is shinier and hence less friction, the air which passes through ball will pass quicker through shiny side in comparison to rough side and Bernoulli's principle states velocity is inversly proportional to pressure, hence there is less pressure on the shiny side which makes ball move towards shiny side.








But I have no idea why does a brand new ball swings, when both the sides are almost same.|||Ashish is more or less correct.





The angling of the seam, and the bowler's action affect the swing of the new ball.





The Australian team don't usually open the bowling with Mitchell Johnson because he often struggles to swing the new ball because of his action.





For more information, have a look at this site.





http://en.wikipedia.org/wiki/Swing_bowli鈥?/a>|||Apart from the answers above: As the ball is getting older due to usage, the fielding side endeavors to keep the shine on one side by repeatedly polishing it. This causes a marginal weight difference and a clever swing bowler keeps the shiny side such a way that when he bowls, the differential weight with the speed and velocity and air friction in the atmosphere causes the ball to move in the wrong direction (reverse). Therefore, very rarely a new ball, which has balanced weight rarely swings in the wrong direction. This could be due to bowlers ability to use the atmosphere to his advantage.|||both conventional swing and reverse swing work on the bernoulli's principle. you are absolutely right about the reverse swing now let me explain you about conventional swing.





have you seen an aeroplane wings at taking off and at landing, the lift force comes from the profile of the wing similarly new ball has prodigious seam and the seam pierces the air to cause differential of velocity and hence pressure , therefore seam position is important for aerodynamic movement of the ball|||I think that the bowlers don't really know themselves. They have actually admitted this.|||couple,moments torques